1. Field of the Invention
The present invention relates to a field emission display device capable of improving light emission uniformity of a phosphor surface (or display surface) of the field emission display device, and a method of manufacturing the same.
2. Description of the Background Art
In general, a field emission display device principally includes a cathode substrate formed with cathode electrodes, an insulating layer formed on the cathode substrate and the cathode electrodes, control electrodes formed on the insulating layer, electron emission material layers received in openings formed through the control electrodes and the insulating layer and formed on exposed portions of the cathode electrodes at the bottom of the openings, and an anode substrate located at the front of the control electrodes and formed with anode electrodes and phosphors (U.S. Pat. No. 3,500,102 (See FIGS. 1 to 4) and U.S. Pat. No. 4,857,799 (See FIGS. 2 and 3)). In the conventional field mission display devices of this type, the openings of the control electrodes are circular in shape.
Some of such field emission display devices further include a shield electrode located between the control electrodes and the anode electrodes and formed with electron pass apertures through which an electron beam flowing from the electron emission material layers to the phosphors passes (Japanese Patent Application Laid-Open No. 2002-324501). In the conventional field emission display devices of this type, the openings of the control electrodes are circular in shape, as described above. Each of the electron pass apertures of the shield electrode is, for example, circular in shape and sized so that all of the opening areas of the corresponding openings of the control electrodes are within the opening area of each electron pass aperture (neither too large nor too small in size) (See FIG. 4 of Japanese Patent Application Laid-Open No. 2002-324501). In this structure, the intensity of the electron beam flowing from each of the electron emission material layers through the corresponding openings of the control electrodes and the corresponding electron pass aperture of the shield electrode to the corresponding phosphor is proportional to the area in which the opening areas of the corresponding openings of the control electrode overlap the opening area of the electron pass aperture of the shield electrode.
In the conventional field emission display devices, the openings through the control electrodes and the insulating layer are formed by a photograph manufacturing process. Specifically, a photosensitive control electrode material layer is formed on the insulating layer, and only portions of the photosensitive control electrode material layer which are to be formed as the control electrodes are exposed to light to change to the control electrodes, while portions to be formed as the openings are unexposed. A developer is caused to flow over the photosensitive control electrode material layer to erode and remove the unexposed portions (to be formed as the openings) of the photosensitive control electrode material layer and portions of the insulating layer corresponding to the unexposed portions, thereby forming the openings through the control electrodes and the insulating layer.
In the field emission display device including the shield electrode, each electron pass aperture of the shield electrode is sized so that all of the opening areas of the corresponding openings of the control electrodes are within the opening area of each electron pass aperture. Therefore, the shield electrode is required to be assembled between the control electrodes and the anode electrodes with high assembly accuracy so that all of the opening areas of the corresponding openings of the control electrodes are within the opening area of each electron pass aperture of the shield electrode without extending off.
Further, if a shift of the assembly position of the shield electrode causes a difference between phosphors in the area in which the opening area of the corresponding electron pass aperture of the shield electrode overlaps the opening areas of the corresponding openings of the control electrodes, variations in the intensity of the electron beam flowing to the phosphors give rise to nonuniform amounts of light emission from the phosphors, resulting in a problem such that the light emission uniformity of a phosphor surface (display surface) of the field emission display device is impaired. Moreover, such defective products lead to increased manufacturing costs.
Furthermore, because the openings formed through the control electrodes and the insulating layer are circular in shape, the reduction in the diameter of the openings makes it difficult for the developer flow to spread to the bottoms of the openings during the formation of the openings. This requires much time for the formation of the openings and makes it difficult to form the openings. For this reason, the diameter of the openings must be large, which results in a problem such that the openings cannot be formed densely, and the intensity of the electron beam decreases.